Cannot read property 'finally' of undefined

I can't figure out why I'm getting an

Cannot read property 'finally' of undefined error here..

$scope.saveToDos = function(){

    console.log("Save to do was pressed.")

    var filteredTodos = $scope.todos.filter(function(todo){

        if(todo.edited){

            return todo

        }

    })

    console.log("There are " + filteredTodos.length + " edited todos")

    dataService.saveToDos(filteredTodos)

    .finally($scope.resetTodoState())

}

this.saveToDos = function(todos){

        var queue = [];

        todos.forEach(function(todo){

            var request;

            if(!todo._id){

                request = $http.post('/api/todos', todo);

            } else{

                request = $http.put('/api/todos/' + todo._id, todo).then(function(result){

                    todo = result.data.todo;

                    return todo

                })

            }

            queue.push(request);

        })

        $q.all(queue).then(function(results){

            console.log("I saved " + todos.length + " todos!");

        })

    }